Very little is known of the phenomenon of phenotypic transformation of epithelial cells, although the majority of human neoplasias arise from cells of epithelial origin. Murine mammary gland cells and the well-characterized tumor virus SV40 have been selected as the model systems to determine the characteristics of transformed epithelial cells and elucidate basic biological events involved. Biological, molecular and genetic aspects of the system will be monitored. The project will analyze the spectrum of growth properties exhibited by BALB/c mammary gland cells exposed to SV40, will compare the interaction of SV40 early proteins with epithelial cell processes, and will examine the influence of endogenous mouse mammary tumor virus (MMTV) sequences on the observed events. This study will expand our knowledge of the biology of SV40 to the mammary cell system and will reveal whether any or all of the vast wealth of information of SV40 interactions with fibroblasts can be extrapolated to epithelial cells. It will promote our understanding of mammary gland neoplasia, in particular, and will have important implications for epithelial cell transformation, in general.